Simple method to correct for pitch in a non 6D couch for a frameless stereotactic treatments

Stereotactic treatments has been in vogue for more than 3 decades and efforts were always made to reduce the errors in delivery by introducing a good number of quality assurance methods. The introduction of volumetric imaging before treatment delivery facilitated frameless stereotactic treatments. But, correcting for rotational errors required 6D couch. However, there are publications which show that 6D couch is an expensive technology and it is one among the many factors that contribute to the accuracy and its absence is not a major factor. In our setup, we have been performing stereotactic treatments with couches which has only translational movements. After introducing volumetric imaging and performing frameless stereotactic treatments, we found that rotational errors also need to be addressed. Out of the three rotational errors such as pitch, yaw and roll, we found that pitch is a rotational correction which is a dominant systemic error, has a significant role and it is addressed in our work